The GET_ENTITYSET method in the data provider class is called when you specify an entity set name without any parameters in the URL, and returns all entities in the specified entity set.

After the runtime data provider class is created, the method is initially an empty shell. The base class implementation does nothing, so the derived runtime data provider class must redefine this method to implement the business logic that enables the service to return entity sets.

GET_ENTITYSET is a general-purpose method for delivering any entity set. The GET_ENTITYSET method in your runtime data provider class responds to requests for any of the entity sets defined in the model class.

To provide the functionality for getting an entity set:
  1. Redefine the GET_ENTITYSET method in the general runtime data provider class to dispatch requests to the GET_ENTITYSET methods data provider classes that are specific to each entity type.
  2. Implement the GET_ENTITYSET methods for each entity-type-specific runtime data provider class.

For a service to provide delta-querying capabilities, its GET_ENTITYSET method must issue a delta token and return it as part of the response. This delta token is picked up by the client and submitted with subsequent requests to retrieve the data that has changed since the token was issued. Add the delta token to the ES_RESPONSE_CONTEXT parameter, which is available in the delta token.

It is up to individual developers to determine the exact format and content of the token; however, it must include the issue time and date.

When a delta token is inserted in the ES_RESPONSE_CONTEXT parameter, it becomes available to the client, in the response header. When the client wants to query the entity set and use the delta functionality, it can pass the delta token in the URL parameter “deltatoken”. For example:

When a delta token is supplied as part of the request, GET_ENTITYSET_DELTA is called to manage the request, and returns only the entities that have been created or changed since the token was issued. See GET_ENTITYSET_DELTA Method.